Cushioning structure for fluid power cylinders



Dec. 11, 1962 R. K. WILLIAMS 3,067,725

CUSHIONING. STRUCTURE FOR FLUID POWER CYLINDERS Filed Feb. 27, 1961 QOODINVEN TOR. ROBERT K. HILL/4M5 BY W A TTOR/VEVS United States PatentOflflce 3,0617% Patented Dec. lll, 1%62 3,667,726 CUSHIONING STRUCTUREFOR FLUID POWER CYLINDERS Robert K. Williams, Akron, Ohio, assignor toInternational Basic Economy Corporation, New York, N .Y., a corporationof New York Filed Feb. 27, 1961, Ser. No. 91,900 4- Claims. (Cl. 121-38)This invention relates to cushioning structures for a fluid powercylinder.

It has always been a problem in fluid power cylinders to properlycushion the piston as it completes its stroke. Cushioning is necessaryto prevent the piston from impacting upon the end of the cylindersresulting in damage to both the piston and the cylinder end. Variousstructures have been employed to accomplish the cushioning function.Some of these structures include springs of various designs placedbetween the plunger and the end of the cylinder. The idea of restrictingthe rate of exit of fluid from the cylinder as the piston reaches thisfinal position has also been employed. Although both of these methodsprovide a degree of cushioning it has been found that they are notentirely satisfactory particularly in providing a long cushioning strokewithout materially increasing the length of the cylinder.

The present invention overcomes the above problems by utilizing atelescoping plug as the fluid cushioning means. This plug can have aspring biasing the plug in extended position so as to provide aresilient cushioning means which becomes operable itself after the fluidcushioning means to further cushion the piston movement. Thisarrangement provides a cushioned stroke for a distance of about 75%longer than current design; however, it does not substantially reducethe distance at which the piston may travel at a maximum rate beforecushioning.

It is therefore an object of this invention to provide cushioning meansfor a fluid power cylinder wherein the length of cushioned stroke isincreased substantially.

Another object of this invention is to provide cushioning means for afluid power cylinder wherein the cushioning means include a resilienttelescoped plug.

A further object of this invention is to provide cushioning means for afluid power cylinder which includes a combination of fluid and resilientcushioning structure.

Yet another object of this invention is to provide cushioning means fora fluid power cylinder wherein the cushioning means is composed of aminimum number of parts which are economical to manufacture and simpleto assemble.

' These and other objects and advantages of this invention will becomemore apparent upon reading the specification in conjunction with theaccompanying drawings.

In the drawings:

FIG. 1 is a fragmentary cross section of a fluid power cylinderemploying the cushioning means of this invention in the fully extendedposition;

FIG. 2 is a fragmentary cross section of a fluid power cylinderemploying the cushioning means of this invention shown in the fullyretracted position.

Basically, this invention is concerned with cushioning means for a fluidpower cylinder. The fluid power cylinder conventionally has closed endsand a hollow chamber in which a piston is free to operate. A piston rodis connected to the piston and extends through an opening formed in oneof the cylinder ends. A bore formed within this one end of the cylinderis provided with a seal mounted extending radially inwardly thereof. Thepiston rod passes through the bore with suflicient clearance to permitflow of fluid ahead of the piston. However, it carries a telescopingplug biased to extended position and adapted when the piston is forcedin a forward direction to engage the seal in the bore. This blocks thenormal flow of fluid from the cylinder through the clearance between thebore and piston rod to the outlet. Consequentially, the fluid thereafteris required to flow through a restricted bypass to the outlet. Thisbypass is provided with a regulator valve which can be adjusted tocontrol the rate of flow of fluid from the cylinder. By restricting therate of flow from the cylinder, pressure will build up within thecylinder, and the piston is thereby fluid-cushioned. The plug continuesto move with the piston rod until it hits the cylinder end which acts asa stop for the plug. The bushing then telescopes into the plug againstthe fluid pressure and against the bias of the spring which normallyseparates the two members. If the spring is made sufliciently strong itwill provide an additional cushioning effect for the piston.

Referring to the drawings which show this structure, the assemblyconsisting of a fluid power cylinder with the cushioning means isdesignated generally as 10. The assembly includes the cylinder 15 withthe end 16, the piston 38 and its rod 40 and the telescoping plugstructure 45.

The closed end 16 is formed of three parts, namely the cap 22, bearingplug 21 and sleeve 25 although it should be understood that this end 16could be constructed of one solid integrated part. As shown, the sleeve25 is secured within the cylinder wall and the cap 22 is mounted on theend thereof in sealed relationship thereto. The plug 21 fits within acentral bore of the cap 22. It has a centrally disposed bore 23 slidablyreceiving the piston rod 46. The sleeve 25 and plug 21, as previouslystated, could be integral parts of the cap 22. Sleeve 25 also has acentral bore 36 with a reduced diameter portion 31 formed by theinwardly extending rib 27. This rib 27 also forms a shoulder 32 againstwhich a special type seal 2? is positioned. This seal 29 is U-shaped incross-section and has a lip 33 projecting radially inwardly beyond theinner diameter of bore portion 31 to provide a seal against the plug 46(FIG. 1) as will be described in more detail hereinafter. It isimportant to note that this lip 33 is inclined radially inwardly andtoward the right (as viewed in FIGS. 1 and 2) so as to permit fluid toflow in one direction into the cylinder but resrict flow in the oppositedirection. The end 16 is provided with a bypass port formed by thepassageways 26, 1'7 and 19. End 16 also has the combined exhaust andinlet port 20. A groove formed in the outer circumference of sleeve 25receives an O-ring seal 30 to prevent escape of fluid between the end 16and the cylinder wall. Seal 35 is provided between piston rod 40 and end16 to prevent escape of fluid between the piston rod 40 and the wall ofthe bore 23.

The piston rod 40 has a trunk portion 41 and a neck portion 42 which issecured in a centrally disposed bore of piston 38 by nuts as shown. Thetrunk 41 of the piston rod 4%) extends through the bore 36 of sleeve 25and the bore formed in the collar 21. As previously stated sufficientclearance is provided between the walls of bore 36 (including reducedportion 31) and trunk 41 to permit flow of fluid therethrough.

The telescoping plug structure 45 is located at the juncture of trunkand neck portions 41 and 42. This structure includes a washer 43surrounding the piston rod neck 42 and abutting the end of the pistonrod trunk 41, a bushing 55 positioned between the washer 43 and thepiston 38, a plug 46 slidably mounted on piston rod 40 and a spring 60biasing the plug in extended position (FIG. 2).

The bushing 55 has an upturned flange 5 7 which engages the piston 38.It is provided with an annular relief beneath the flange 57 to receivean O-ring seal 44 which prevents fluid from passing between the bore inthe piston 38 and the piston rod neck 42.

The plug 26 has a bore 48 slidably receiving the trunk 41. It has atapered nose for purposes which will be enemas explained more fullysubsequently. The other end of the plug 26 is provided with an annulargroove 47 adapted to receive one end of the spring 6%.

The bore 48 of the plug has an inwardly projecting annular shoulder 49slidably mounted on the bushing 55. This shoulder operates as a stop tolimit the forward movement of the plug. The bore 48 is also providedwith an annular groove receiving an O-ring seal 50 and a retainer lip 51which maintains the O-ring seal 50 in position. This O-ring 5E5 engagesthe plug 48 and the bushing 55 and prevents fluid from passing betweenthe members.

The spring 66 of the coil type surrounds the bushing 55. One end of thespring 6% is received by the annular groove 47 formed in the plug 46 andthe other end of the spring surrounds the flange 57 and abuts the piston38. The spring 6%, constantly urges apart the plug 46 and bushing 55.This spring can be made sufliciently strong to supplement the cushioningeffect of the fluid.

Operation In operation, the piston rod 40 of the fluid power cylinder 1%is connected to some type of mechanism to be actuated. The piston rod 46is reciprocated by applying fluid to alternate sides of the piston byconventional mechanism (not shown). Thus, the piston 38 is protracted,or moved toward the left as shown in FIG. 1, by applying fluid to theright side of the piston 38. The piston rod 4% is retracted, moved tothe right as viewed in FIG. 2, by applying fluid pressure to the leftside of the piston 38.

The cushioning means of this invention is shown only on the left side ofthe piston 38. However, it is to be understood that within the broadestaspect of this invention the cushioning means of this invention may beutilized on both sdes of the piston.

As the piston rod 44 is protracted the piston 38 approaches the cylinderend 16. Since the plug 46 is carried by the piston rod 46 the noseportion thereof will eventually engage the lip 33 of seal 29 and beguided therein by the tapered nose. This blocks the flow of fluid fromthe interior of the chamber through the bore 36 to the outlet port andrequires the fluid to seek a different exhaust path from the cylinder.As a result the fluid is exhautsed through the bypass in the end 16which includes the passageway 26 formed in sleeve 25, and passageways 17and 19 formed within the cap 22. The bore 36 within the sleeve is ofgreater diameter than the plug 46 which aflords an annular space tocomplete a flow path to the port 28*. By restricting the flow of fluidfrom the cylinder the pressure within the cylinder is increasedproviding an air cushion for the piston 38. The degree of air cushioningcan be regulated by the valve member 18.

As the piston rod continues to protract the plug 46 moves therewithuntil its nose engages the cylinder end 16 which prevents furthermovement. Notice that the plug 46 is in continuous contact with the seal29 from the time it engages the seal until it abuts the cylinder end 16providing for a continuous air cushion during this interval of travel.

When the plug 46 is stopped the piston rod 40 continues to move relativeto the plug 46 causing the bushing to telescope within the plug 46against the compression of spring 6t). During this telescoping movementthe fluid cushioning is continued. Further, the piston 38 is furthercushioned by the spring if it is made sufliciently strong. However,within the broader aspect of this invention the spring need not besufliciently strong to produce any eflective cushioning.

When the spring is substantially fully compressed the piston 38 engagesthe end of sleeve 25 which stops further movement. The protraction ofthe piston is now complete and the piston 38 can come to rest gentlyagainst the end of Sleeve 25 as a result of the cushioning means.

The piston 38 and piston rod 40 are retracted by applying fluid pressureto the left side of the piston 38 through the port 20 and past the lip33 of seal 29 which flexes and opens a passageway when pressure isapplied from the left as viewed in FIGS. 1 and 2. As the piston 38retracts the spring 6%) expands separating the plug 46 and the bushing55. This causes the washer 43 on piston rod neck 42 to engage theabutment shoulder 49 on plug 46 and carry the plug with the piston rod.The lug 46 and bushing 55 are completely withdrawn from the sleeve 25and seal 29 as shown in FIG. 2. The cushioning plug is now in positionfor another stroke of the fluid power cylinder.

It can be seen that the invention disclosed herein provides an extremelyeffective cushioning arrangement for a fluid power cylinder. Byutilizing the telescoping plug, cushioning can be obtained during a muchgreater part of the piston stroke without sacrificing space within thecylinder. Thus, more eiiective cushioning is obtained within the samedistance of piston travel than was previously possible. The cushioningmeans utilized herein is constructed of a minimum number of componentparts and is therefore economical to manufacture and assemble.

While a preferred embodiment of this invention has been described, itwill be understood that modifications and improvements as incorporatethe principles of this invention are to be considered as included in thehereinafter appended claims unless these claims by their languageexpressly state otherwise.

I claim:

1. Cushion structure for a fluid power cylinder comprising: a closedcylinder; a piston and piston rod operable in said cylinder, a cylinderend including a bore having seal means; an outlet port communicatingwith said bore; said piston rod carrying a telescoping plug; meansbiasing said plug to an extended position with respect to said piston;restricted bypass means communicating with said cylinder and outletport; movement of said piston in one direction causing said plug toenter said bore and engage said seal thereby preventing fluid fromflowing through said bore to said outlet and providing fluid cushioningfor said piston, said plug when first entering said bore starting saidcushioning, and then abutting said cylinder end for a period of timecausing said plug to be retracted against said biasing means to providefurther cushioning of said piston.

2. Cushion structure for a fluid power cylinder comprising: a closedcylinder, a piston and piston rod operable in said cylinder, a cylinderend including a sleeve portion having an inwardly projecting annular ribdefining a bore, seal means seated against said rib, said piston rodhaving a trunk portion and a neck portion, cushion means including aplug slidably disposed on said trunk portion and a bushing surroundingsaid neck portion and disposed between said trunk portion and saidpiston, said plug having shoulder engaged by said trunk portion forcarrying said plug when said piston is moved in one direction, springmeans received between said plug and said bushing urging said membersapart, an outlet port formed in said end, movement of said piston in theother direction causing said plug to enter said bore and engage saidseal means preventing normal flow of fluid through said bore to saidoutlet, fluid bypass means to said outlet to restrict the flow of fluidto said outlet thereby increasing the pressure within said cylinder tocushion said piston, said plug being adapted to move further into saidbore and engage the cylinder end for a period of time during which it isforcibly retracted over said bushing against the bias of said spring,and thereby provide continued cushioning of said piston.

3. Cushion structure for a fluid power cylinder comprising: acylindrical chamber; a piston and Piston rod operable in said chamber;said chamber having an end with a centrally located bore communicatingwith an outlet port and said chamber for exhausting fluid from saidchamber; a telescoping plug reciprocally mounted on said piston rod andaligned with said bore; said plug having a diameter slightly smallerthan said bore to be received therein to restrict flow [from saidchamber to said outlet port; a restrictor passage means for passingfluid from said chamber to said port in a restricted manner while saidplug is located in said bore; said plug being slida bly movable betweenan extended position away from said piston and a retracted positionadjacent said piston; said plug being normally extended and adapted toenter said here as said piston approaches said end whereby a cushioningeffect is begun; said plug being adapted to move further into said boreand against said end with continued piston movement; said plug beingReferences Cited in the file of this patent UNITED STATES PATENTS2,556,698 Loewe June 12, 1951 2,815,004 Droman Dec. 3, 1957 FOREIGNPATENTS 746,696 Great Britain Mar. 21, 1956

